In conventional negative ion generating devices, negative ions are generated by applying a high voltage generated by a high voltage circuit to separated electrodes, and as a result generating electric discharge via an air pocket interposed therebetween; by emitting electrons of negative charges in the air through electric discharge at a surface of insulator between electrodes which in turn negatively charges water vapors and etc. in the air; or by irradiating surfaces of gold or platinum with ultraviolet ray to emit electrons in the metal to the air which in turn negatively charges the water vapors and etc. in the air. (see, for example, Japanese Patent Laid-open No. 2001-338744)
However, conventional negative ion generating devices employing electric discharge have drawbacks while generating negative ions such as generation of byproducts such as harmful ozone and a high voltage circuit for generating electric discharge employed therein poses a danger of electrocution and a fire. Moreover, in a case of ultra violet ray irradiation method, one has to exercise extra caution to avoid irradiation of harm ultra violet ray on oneself, e.g., the eyes.